Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B5/00—Measuring arrangements characterised by the use of mechanical techniques
  • G01B5/0002—Arrangements for supporting, fixing or guiding the measuring instrument or the object to be measured
  • G01B5/0009—Guiding surfaces; Arrangements compensating for non-linearity there-of
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
  • G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
  • G01B21/04—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness by measuring coordinates of points
  • G01B21/042—Calibration or calibration artifacts

Definitions

• the invention relates to a method for determining the geometric accuracy of a linear guide which has a slide which can be displaced in one direction of a spatial coordinate system and consequently as a rigid body system with a degree of freedom 1 (linear) and with at most five individual deviations consisting of Rolling (EAX), pitch (EBX), yaw (ECX), straightness Y (EYX) and straightness Z (EZX) is considered by determining these individual I deviations.
• EAX Rolling
• EBX pitch
• ECX yaw
• EYX straightness Y
• EZX straightness Z
• Linear guides are used in many machines and machine parts.
• the machine tools represent a large field of application.
• the guides secure movements of machine parts against one another in a specific, preferably straight path and are designed either as sliding guides or Ro II guides.
• Another type of guide are the right-hand guides, which define the changing positions of machine parts with respect to one another, for example a tailstock on a machine bed or a counterhold for milling machines.
• the invention is concerned with the measurement of such guides mentioned above, these measurements should allow a statement about the quality, ie the accuracy of the guide len.
• the measurements are limited to linear guides, which make up the largest part of the guides used. The purpose of these measurements is to determine the geometric accuracy of a linear guide.
• a rigid body In three-dimensional space, a rigid body has six degrees of freedom with three translations and three rotations.
• a linear guide can therefore, viewed as a rigid body system with a degree of freedom 1 (linear), have a maximum of five individual deviations, for each reference there would be two translations and three rotations. The values of these five individual deviations fully describe the geometric accuracy of a linear guide.
• the linear guide is assigned a measuring base approximately parallel to its direction and a measuring device is attached to the guide which carries five length measuring sensors by means of which the measuring base is scanned, one for Measuring point of the guide in one position five distances measured simultaneously in two mutually perpendicular planes and the individual deviations are then calculated.
• FIG. 1 is a coordinate system for presen- tation of the names (according to ISO), Flg. 2 shows a schematic illustration of a
• FIG. 3 is a schematic representation of the complete measurement of an internal guide in the form of a stiffness map
• Fig. 4 is a schematic presen- tation of a
• FIG. 5 shows the stiffness map of the measurement on the machine according to FIG. 4.
• Fig. 1 the coordinate system with the six degrees of freedom for a rigid body and the corresponding short names are shown. If the linear guide to be measured is placed in its longitudinal extent in the X-axis, the designations shown in FIG. 1 result for the same deviations. With these five deviations, the geometric accuracy of the guidance can be fully described. According to the Maxwe I I 'see theory, also called kinematic construction principles or 6-point theorem, it is sufficient to record five measurement variables for each measuring point in a linear guide in order to be able to calculate the individual deviations therefrom.
• FIG. 2 a device is shown schematically in FIG. 2.
• a linear guide 1 to be measured for example a
• a machine arm 2 is attached to the machine bed 2 of a machine tool and a slide 3 that can be moved on the bed 2.
• the measuring arm 4 is supported on a base 5 which is fastened on the slide 3, for example by means of a magnet.
• the measuring arm 4 and the base 5 are constructed in such a way that they can be regarded as rigid.
• the measuring arm 4 carries at its free end a measuring head 6 which is designed as an angle with two legs 7, 8 arranged at right angles.
• the measuring head 6 is assigned to a measuring body 9, which serves as a measuring base.
• the measuring body 9 is set up approximately parallel to the linear guide 1.
• the length measuring sensors 10 are mounted in the measuring head 6, two of which are arranged in the vertical leg 7 and three in the horizontal leg 8 of the measuring head 6. However, it is possible to arrange the length measuring sensors 10 in a different way. In order for the inductive or capacitive length measuring sensors 10 to lie against the measuring body 9 within their displacement path, it is aligned approximately parallel to the linear guide 1.
• the connection I lines 12 of the sensors 10 are connected to a switch 13 which connects the individual sensors 10 to a computer 15 via a line 14.
• the respective measuring position 20 of the measuring arm 4 is also transmitted to the computer 15 via a position sensor 17.
• 16 denotes a device, for example a printer or a plotter, on which the values calculated by the computer 15 are shown.
• FIG. 3 Such an expression by means of a plotter is shown schematically in FIG. 3.
• the values EAX, EBX, ECX, EYX and EZX according to FIG. 1 are shown on the X axis, which corresponds to the length of the linear guide. These five curves are collectively referred to as a rigidity map.
• Frg. 4 and 5 is a practical example of such a measurement.
• a bed milling machine is shown, on the cross arm of which the measurement is carried out in the X-axis.
• the measuring arm (not shown) is in this case attached to the spindle 21 and is slidably mounted on the horizontal linear guide 22.
• the horizontal linear guide 22 is supported on the displaceable stand 23, while the measuring body (not shown) is set up on the stationary bed 24.
• the measuring arm thus projects downward and, with the measuring head, engages around the measuring body mounted on the bed 24.
• FIG. 5 The result of this measurement is shown in FIG. 5 in the form of a stiffness map. It can be seen from this that the measurements were carried out several times during a back and forth movement.
• the graph for ECX shows the deflection of the guide 22 when the lockers I see 21 reach the end of the guide 22. In this diagram, hysteresis phenomena are also the most fixed Ibar.
• the five individual deviations depend on the individual probe positions with respect to the measuring point 20, on which the individual deviations are calculated.
• This point is usually where the base 5 of the measuring arm is attached. However, this point can also be set at any other position, i.e.
• the geometry of the measuring device can be determined by the software of the computer provided that the connections are rigid.
• the absolute accuracy of the sensors depends on the measuring path with regard to the measuring point, whereby the repeatability is mainly due to the mechanical construction of the sensors, e.g. , through the
• the measuring body 9 must be fixed in such a way that a displacement is not possible even with the smallest forces
• the measurements for setting up a rigidity card can be carried out in three different ways.
• the simplest measurement is done manually, whereby the approach to the measuring point and the triggering of the measurement apparatus l is carried out.
• With automatic static measurement the measuring position is approached and then the measurement is carried out, whereupon the next measuring point is approached. The whole process is done automatically.
• Schi iessl I can record the measured values while the sled is moving, which is also called flying measurement.
• the application of the invention is not limited to the measurement of a linear guide. Basically, all systems that have linear guides or can generate linear movements, e.g. multi-axis systems such as robots can be measured. For this purpose, such a system is strongly connected to the measuring head of the measuring device. The system's deviations from the linear movement are recorded analogously to the measurement of linear guides described,

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Length Measuring Devices With Unspecified Measuring Means (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4188815

Family Applications (1)

Country Status (2)

Cited By (2)

Citations (3)

• 1987
  • 1987-02-12 CH CH51787A patent/CH672548A5/de not_active IP Right Cessation
• 1988
  • 1988-02-08 WO PCT/CH1988/000029 patent/WO1988006271A1/de unknown

Patent Citations (3)

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